1. Field of the Invention
The invention is directed to a thread tensioning device for use on a lock stitch sewing machine in a thread handling system wherein needle thread is caused to pass between elongate members of a thread holder which meters thread to the looptaker of the machine.
2. Description of the Prior Art.
A thread handling system of the described type may be seen, for example, in U.S. Pat. No. 4,356,781 for "Thread Handling Arrangement for Sewing Machines" of Donald Rodda, issued Nov. 2, 1982. Thread demanded by the looptaker in such a system is obtained from the elongate thread engaging members of a thread holder, and from a thread tensioning device. However, difficulties arise due to the restraint imposed on the thread by the tensioning device as it is being withdrawn therefrom by the looptaker. Such restraint results in a shortage of thread at the looptaker and the premature cast off by the looptaker of a loop of thread on a side of the bobbin case from which it can not be withdrawn by the takeup of the machine into a proper stitch, but can only be broken or sewed into a garment leaving a large loop.
It is a prime object of the invention to prevent the premature cast off of thread from the looptaker of a lock stitch sewing machine on account of restraint applied to the thread by a thread tensioning device in a thread handling system as described.
It is another object of the invention to provide an improved thread tensioning device through which thread can fall without restraint to supply thread to a looptaker in a thread handling system as described.
Other objects and advantages of the invention will become apparent during a reading of the specification taken in connection with the accompanying drawings.